[GHC] #7684: cgrun071 segfaults

[GHC]

#7684: cgrun071 segfaults
----------------------------------+----------------------------------
        Reporter:  tibbe          |            Owner:
            Type:  bug            |           Status:  infoneeded
        Priority:  normal         |        Milestone:  7.8.1
       Component:  Compiler       |          Version:  7.7
      Resolution:                 |         Keywords:
Operating System:  MacOS X        |     Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash  |       Difficulty:  Unknown
       Test Case:  cgrun071       |       Blocked By:
        Blocking:                 |  Related Tickets:
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Comment (by tibbe):

 Now I'm confused. Both GCC 4.2 (apple-gcc42 from Homebrew) and GCC 4.9
 create the correctly zero extended code for `hs_popcnt8`:

 GCC 4.2
 {{{
 #!asm
 _hs_popcnt8:
 LFB112:
         pushq   %rbp
 LCFI0:
         movq    %rsp, %rbp
 LCFI1:
         movzbl  %dil, %edi
         leaq    _popcount_tab(%rip), %rax
         movzbl  (%rdi,%rax), %eax
         leave
         ret
 }}}

 GCC 4.9:
 {{{
 #!asm
 _hs_popcnt8:
 LFB110:
         leaq    _popcount_tab(%rip), %rax
         movzbl  %dil, %edi
         movzbl  (%rax,%rdi), %eax
         ret
 }}}

 Exact GCC versions:
 {{{
 $ gcc-4.2 --version
 i686-apple-darwin11-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5666) (dot 3)
 ...
 $ gcc-4.9 --version
 gcc-4.9 (GCC) 4.9.0 20140223 (experimental)
 ...
 }}}

 Perhaps this bug was fixed in some release of GCC 4.2?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7684#comment:48>
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